3 Simple Ways to
Share What You Make

With Instructables you can share what you make with the world — and tap into an ever-growing community of creative experts.

PhotosPhotos

Share one or more photos of a project, recipe, or whatever you've made, quickly and easily.

Step by StepStep-By-Step

Share your step-by-step photos with text instructions of what you made so others can do it too!

VideoVideo

Share your how-to video. You'll need your embed code from a video site such as YouTube.

70mm refracting telescope

70mm refracting telescope
My son wanted a little telescope.  The optics for this 70mm F/4.3 one were bought on CloudyNights.

The tube is 1/8" thick card-board tubing, impregnated with a mix of Titebond II and water.  The front wider tube holds the lens in place (and there is an inner card-board retainer).  I made the wider tubing by cutting a section of the normal tubing and gluing in a curved segment.

The focuser is a low-profile home-made Crayford-style wooden focuser with PTFE bearing surfaces.  See here.

Unfortunately, only a very light eyepiece works balance-wise in the mount as originally constructed (first photo).  The scope was too small for its Dobsonian-style mount, and moved up and down too easily.  

I modified the mount as in the next photos, by adding a tension adjust on one side.

The third photo shows the right altitude bearing. The nut is superglued in place. If it ever comes unglued, I'll glue something on top of it to keep it in place, or replace it with a threaded insert, or think of something else. The nut actually was a locknut, but I cut out a lot of the locking plastic, so its locking action is very mild.

And the last photo shows the inside of the mount. The black ring is a superglued fiberglass washer. On the other side, under the knob (you can kind of see it in the first photo) there is a superglued washer made from milkjug plastic (rough side facing the wood) so the knob doesn't come undone.
1 comment
Mar 4, 2012. 12:07 AMtholopotami says:
Nice! I liked the simplified Crayford and the idea to cover the tube with Titebond. I'll keep this in mind.

Pro

Get More Out of Instructables

Already have an Account?

close

All Steps Viewing
View all steps of an Instructable on the same page when you're a Pro Member.

Upgrade to Pro today!
25
Followers
18
Author:arpruss